Photochromographical process



Jan. 27, 1925. 1,524,499

L. BASSANI PHOTOCHROMOGRAPHI CAL PROCESS Filed June 23, 1920 INVENTORL LAURENT BASSANI AT ORNEY Patented Jan. 27, 1925.

UNITED STATES LAURENT BASSANI, 0F NE'UILLY-SUR-SEIN E, IRAN rnorocnnomoeaarmcar. racemes.

Application filed June 23, 1920. Serial No. 391,118.-

To all whom it may concern:

Be it known that I, LAURENT BAssANI, subject of the King of Italy, residing at 4 Rue dArmenonvllle, Neuilly-sur-Seine, Seine, in the Republic of France,have invented new and useful Improvements in Photochromographical Processes, of which the following is a specification.

My invention relates to improvements in photochromographical processes.

In the reproduction of colored pictures, photomechanical processes have been long used in lithography for selecting colors in combination with the use of a reticulated screen. It was thus possible .to reduce to a' minimum the laborof the s ecialists or closed the following- 'methods.

chromists who formerly eifecte by hand the selection of the colors. This process then made it possible to execute with 4, 5 or 6 colors which in ordinary lithography would necessitate 10,- 12 or 14 colors, i. e. 10, 12 and 14 roofs of the same design.

xperts have however acknowledged that important improvements have still to be made in said industrial printing methods.

Researches in connection with the printing of large numbers of prints have disdifiiculties: First it was. necessary to use a special paper or couched paper and second, in order to obtain delicacy and vigor in the print, it was necessary to have recourse to photogravure The above disadvanta were apparently removed. by the use of t e ofi'se printing machines which enable any number of prints to be runoff on any desired rained paper or on fabrics (linen, cloth, p ush, silk, etc). However this condition was only possible by faithful execution of the following prelimv inary steps:

Preparing good photomechanical reticulated plates.

1 {ransferringon copper by exposure to Transferring directly or through an intermediate surface upon a lithographic stone.

' Transferring through an intermediate surface upon the printing-plate of the machin especi y in the light parts of the picture e. The photogravure operation appeared a removes all delicacy from the image and is detrimental in obtaining half-tones and shadings whereby the prints lack in sharpness and even in vigor;

The present invention has for its purpose to remove said difliculty. It permits to dispense with adjusting or retouching the net on the picture by subsequent operations such asin photogravure and to obtain the dwired result by purely photomechanicalmeans. It thus permits to transfer directly suitably reticulated photographic plates by exposure to light upon any lithographic surfaices (stones, zinc, etc.) which after being prepared as usual (by inkin gumming, 'aeidifying, etc.) can be used for printing either by transfer or directly. 7

By means of the invention, an important economy, is thus realized in time and materials. It permits to use the offset machines to the best advantage and to obtain on thesame, considerable numbers of prints upon any desired paper, fabric, etc.

The improved method essentially consists in taking from the original whatever it may be (water colour, printing or real subject) for one and the same color and in identical conditions, two photographic plates which The first plate is'strong, so far as dura tion of exposure and developing are concerned so-that the thinnest details and-the lightest shades of the original will appear. It is obtained by arnanginga suitable screen in the camera in front of the sensitized plate and progressively shifting said screen horizontally along the axis of the camera during the exposure.

The second plate is taken in the same conditions, but the screen is subjected during exposure to an axial and a transverse displacement, which latter is preferably vertical.

The above displacements, which are independent of the variation in the initial position of the screen as indicated in textbooks on physics will, so to speak, effect a mechanical selection of the parts of the net which are to be preserved from those which should be'reduced or removed.

The accompanying drawing. shows diamounted in a frame which may be shifted horizontally along the axis of the camera when a micrometric screw 6 is rotated and vertically when another micrometric "screw 7 is actuated.

The construction of the actuating mechanism for operating the screencomprises the screws 6 and 7, maintained at their ends in the frame carrying the screen, the screws bei screwed respectively in the nuts 12 uifd dd The nut 12 is slidably mounted in t e groves 13 formed in the side walls of the aperture 14 provided in the lower wall of the camera. The nut 15 having a square outer section is slidably mounted in agroove 17 of the framesupporting the sensitized plate; said nut is lateralymaintained by two cheeks 16 bearing on said latter frame andis prevented from rotating about itself by the outer. square section thereof. Y

It is pointed out that the vertical displacement of the nut 16 under the action of screw 7 is very small. The displacement which is necessary to bring a line of the screen to the position formerly occupied. by

the next line is at most 1/50 of an inch, i; 'e.

thehcoarsest screens have 50 lines to the 111C 4 Figs. 2 and 3 show on a larger scale the 4 paths of the light raysin the camera in accordance' with the displacements of the screen. Fig. 2 relates to the first photographic plate andFig. 3 to the second.

In taking the first plate which should fur.- nish an image upon which allthe details will appear, the screen 4 is shifted progressively during exposure, by means of the screw 6 in an axial direction as shown by the arrow f. A maximum reduction of the net is thus obtained even in the lighest shades. Fig. 2 shows that when the screen 4 is shifted fro-mpositionA to position B,

any light beam 10 issuing from a point 3 of the screen 3 and obturated by the part 9 of the screen is shifted to the position shown at 8 in dotted lines, so that the unexposed part a b.0f the plate is substantially reduced to a b. It is thus seen that by a displacement of the screen in an axial direction', as'explained, the not produced on the sensitized plate can be reduced in any desired propo'rtion.

. In obtaining the'second p1ate,.which will furnish the dark shades andthe junction thereof with the medium s'hades, the Screen is shifted during exposure in a horizontal the screen is shifted from position A to 100- sition B the part c d of the sensitized plate which was shielded from the influence of the light rays by the screen is subjected on its turn to the. action of said rays on its whole part dul the remaining part 0d alone bein not touched by the beam issuing from t e point 3 of the diaphragm 3.

,It is obvious that'said part cal may be reduced as much as wanted by shifting the screen in sufiicient proportions. Instead of a vertical displacement, a transverse displacement might also be im parted to-the screen.

Said displacements can be effected either once or a plurality of times accordin to the effects sought for or the character 0 the ori inal to be reproduced.

he reticulated plates obtained are then treated by usual means and the images can i be transferred by exposure to light onto any printing surfaces: stone, zinc, etc.

It is to be-understood of course that the present invention may be applied in black my process contemplates obtaining by photomechanical means, images having very pure whites and strong blacks, the images giving at'the same time all of the details of the model. This problem consists in eliminating the black points left by the net or screen in the whites of the photographic plate without in any way im airing the details or causing the latter to dlsappear; it might be said on the contrary that the present processv conserves all the details of the image with- .out reducing the intensity of the blacks.

The method according to the invention consists in preparing for each object to be photographed, two photographic plates which, as stated will eachserve for obtaining a separate printing plate. The final printing will be effected upon the sheet of paper or other material with said two printng plates by successively ap lying the latter in such manner that the nal reproduction of the subject will consist of the superposition onthe sheet of paper or the like of the two printso'btained with said print- 1ng lat/es. The first of ..the said photograp- 1c plates may be obtainedlin the usual manner and if desired a slight displacement may be g1ven to the screen in the direc- Ill 4 displacement being effected by adjustment of the screw 6.

The second photographic late is obtained by shifting the screen a ong the axis of the camera if desired, but it is particularlyessential that the screen be adjusted in its own plane, i. e. in a plane perpendicular to the said axis, in the present instance the plane referred to being vertically disposed.-

The efi'ect which is obtained by this dis placement of the screen in a plane perpendicular to the optical axis of the camera may be explained, as follows, with particular reference. to Figure 3; the positions of the screen 4 indicated A and B and spaced slightly apart along the said axis for the sake of clearly illustratin the invention, show the openings t through which the projected rays of li ht ass. The-full lines show the path 0 lig t rays governed by the A? position of the screen, while the dotted lines show the path of the light rays in the adjusted position B of the screen. The

screen 4 is disposed in its lowermost position A during the greater part of the exposure, the rays passing through the opening t will illuminate the sensitized plate on a portion indicated 7. g. which as is well known in the photogravure art,. ives upon the final print a white circle. Vhen the screen is shifted from position A to B, the ortion of the plate behind the opening t w ich is now acted upon by the rays, is designated f 9 whereby the whole surface acted upon is f g. The result on the final print is a slight translation of the white circle. Regarding the translation on the light and dark portions of the image, which portions correspond to the lighted and dark portions of the model, it will be apparent that the small black dots corresponding to the unaffected parts of the sensitized plate will disappear.

It will be seen that the first plate obtained without any displacement of thescreen or with a slight displacement thereof alon the optical. axis of the camera, will give a the fine details of the model, but the result obtained will have neither strongwhites nor strong blacks. On the contrary, in the second plate obtained by adjusting the screen in its own plane, the black dots have entirely disappeared from the white portions, while the dark portions have been but very slightly affected by the displacement of the white circles, in which case the dark por- ;-tions have still retained sufficient intensity.

Subsequent printing both images on the same sheet of paper or the like will present the black dots from the first plate only while the blacks will be further strengthened by the superposition of the black portions of both images.

The desirable results thus obtained are made possible by shifting the screen in its own plane, 1. e. perpendicularly to the optical axis of the camera.

Having now described my invention, what I claim as new and desire to secure byLetters Patent is:

1. The herein described method of making negatives from which printing plates may be produced, which consists in making successive exposures of sensitized surfaces through a screen, and shifting the screenafter the first exposure in a plane at right angles to the axis of the camera.

2. The method of making negatives from which printing plates may be produced which consists in making successive exposures through a screen of superposable sensitized plates, and shifting the screen during the exposure of the second plate in a plane at right angles to the axis of the camera.

3. The method of making negatives from which printing plates may be produced which consists in making successive exposures throu h a screen of two superposable sensitized plates, shifting the screen progressively away from the sensitized surface during exposure of the first plate in a direction parallel to the axis of the camera, and thereafter shifting the screen during the exposure of the second plate in both an axial and transverse direction with respect to the axis of the camera.

= In testimony whereof I have signed my name to this specification.

LAURENT BASSANI. 

